Until recently, hospitals have had little financial incentive to minimize readmissions as Medicare pays for all hospitalizations based on the diagnosis, regardless of whether the admission is an initial hospital stay or a readmission.15
However, recent policy developments indicate that this culture is changing. In 2007, the Medicare Payment Advisory Commission (MEDPAC) proposed mandatory reporting of risk-adjusted readmission rates, with eventual penalties for hospitals with high rates.15
In 2009, CMS began requiring hospitals to report 30-day readmission rates for patients with several medical conditions.16
These increased reporting requirements may reflect the recognition that readmissions not only lead to increased health care utilization and expenditures, but are also often preventable. Because rehospitalization has clear links to health care costs and modifiable processes of inpatient care, health services researchers, policy makers, and payers have increasingly used readmission as a quality-of-care measure.2, 17, 18
Information on predictors of readmission are needed for the development of interventions that will decrease readmissions and improve patient outcomes.
Colon cancer is a cause of significant morbidity and mortality. 148,000 new cases of colorectal cancer are diagnosed annually in the United States.19
Surgical resection performed in the in-patient hospital setting is the standard of care for localized disease. Despite the high incidence of colon cancer and the frequency of surgical treatment, the rate and predictors of readmission after colon cancer surgery have not previously been systematically studied using population-level data. Previous studies have consisted of single-institution retrospective case series. In these reports, which have often combined patients with benign and malignant disease, readmission rates range widely, from zero to 27 percent.5, 20–36
Only one previous study, by Goodney and colleagues, was based on population-level data.5
In the current study we used the Surveillance, Epidemiology and End Results (SEER)-Medicare linked database to determine the rate, causes, and consequences of readmission after colectomy for cancer. We found that 11.0% of patients—almost one in nine—were readmitted within one month of discharge. Most readmissions occurred within the first 10 days after discharge.
The most common readmission diagnoses were ileus/obstruction and other gastrointestinal complications, surgical site infection, pneumonia and other respiratory complications, bleeding and anemia, and sepsis. After adjusting for other factors, significant predictors of 30-day readmission included male gender, Asian race, hospitalization in the prior year, comorbidity, emergent admission, low hospital procedure volume, prolonged length of hospital stay, perioperative blood transfusion, associated ostomy, post-operative complication requiring an additional procedure, and discharge to a skilled nursing facility. Furthermore, we found a striking association between 30-day readmission and one-year mortality, comparable to other well-established predictors of mortality such as old age and advanced cancer stage. Many of the variables that predicted readmission were also significantly associated with one-year mortality.
The SEER-Medicare database has several advantages for the study of readmission. It contains information on a wide array of patient-, disease-, and treatment-related factors. Results based on national-level SEER-Medicare data may be more generalizable to the population at large compared to findings from studies conducted at specialized academic medical centers. Importantly, SEER-Medicare allows the tracking of patients from one hospital to another. Therefore, we were able to detect readmissions to any hospital, not only readmissions to the hospital where the original surgery was performed. We found that over 13% of readmissions were to another hospital. Single-institution retrospective studies are likely to underestimate the rate of readmission. CMS and other payers should be cognizant of this risk of underestimation before implementing programs based on self-report by hospitals or providers.
The rate of rehospitalization in our study population was almost identical to the readmission rate of 11.1% calculated by Goodney and colleagues for patients with colon cancer treated with colectomy in their analysis of national Medicare data from 1994–1999.5
Higher population-based readmission rates have been reported for coronary artery bypass surgery and other complex cancer operations such as pneumonectomy, esophagectomy, and pancreatic resection.5, 37
In the year 2000, approximately 96,300 colon cancer resections were performed in the United States, and by 2020 this figure is predicted to increase to 141,100 operations.38
Clearly, a readmission rate of almost one-in-nine for patients undergoing this common procedure represents a significant problem from a clinical, public health, and health policy perspective.
We found that most readmissions after hospitalization for colon cancer surgery occurred on the day after discharge and shortly thereafter. The median day of readmission was post-discharge day nine. This is consistent with previous studies which have shown that hospital readmissions cluster shortly after discharge and then decline in frequency.2, 23, 32
Readmissions that occur soon after surgical discharge are likely to be related to surgical complications, poor discharge planning, or other modifiable factors.
Our study included an analysis of the reasons for readmission. The most common causes of readmission were ileus/obstruction and other gastrointestinal complications, surgical site infection, pneumonia and other respiratory complications, bleeding and anemia, and sepsis. These clinical entities are all potentially preventable complications of surgical care. Similarly, an analysis of coronary artery bypass graft surgery in New York found that 85% of readmissions were directly related to potentially preventable surgical complications.37
Our findings regarding the timing and causes of rehospitalization support the use of 30-day readmission as a quality-of-surgical-care indicator.
In their study on early readmissions in the Medicare program, Jencks and colleagues concluded that over 70% of readmissions after surgical discharges were due to “medical conditions”.1
However, in patients who underwent “major bowel surgery,” they reported the most frequent reasons for rehospitalization were “GI problems” (15.9%), postoperative infection (6.4%), “nutrition-related or metabolic issues” (5.6%), and GI obstruction (4.3%). Rather than medical conditions, we would characterize these readmission diagnoses as potentially preventable surgical complications, which is consistent with our findings regarding the causes of readmission after colectomy for cancer.
While numerous investigators have estimated the readmission rate after colorectal surgery, relatively few have identified predictors of readmission. In a prospective, multicenter study of 1,421 patients undergoing colorectal surgery in France, Guinier and colleagues identified five statistically significant predictors of readmission: surgical field contamination, long operative duration, need for an additional surgical procedure, low hemoglobin, and lack of air leak testing of the bowel anastomosis.31
Kiran and colleagues at the Cleveland Clinic conducted a retrospective study to identify predictors of 30-day readmission after colorectal surgery for benign and malignant disease. They found two variables that were significantly associated with readmission: longer hospital stay and use of corticosteroids.32
In contrast to the French multicenter study, low discharge hemoglobin level was not a significant predictor of readmission. Another single-institution study by a group in Allentown, Pennsylvania, did not yield any significant predictors of rehospitalization after elective colorectal surgery, leading them to conclude, “readmissions after colorectal surgery cannot be predicted”.22
However, this study was limited by a relatively small sample size (n=249).
To our knowledge, the current study is the first to identify predictors of early readmission after colon cancer surgery in a population-based sample. Our multivariate analysis identified several significant predictors of readmission after colon cancer resection in this cohort of Medicare beneficiaries aged 66 and older. The odds of readmission were higher for males than females. Gonzalez and colleagues, in a prospective cohort study, also reported a significantly higher risk of readmission in men versus women treated for colorectal cancer in Spain.39
Similarly, in a study of Medicare beneficiaries who underwent surgical treatment of colorectal cancer, Morris et al. found an elevated relative risk of post-operative complications requiring procedural intervention in males compared to females.13
We adjusted for post-operative complication in our multivariate model, yet the increased odds of readmission for males persisted.
Black-white racial disparities in risk factors, screening, stage at diagnosis, treatment, and outcomes such as mortality have been extensively documented for colon cancer patients.40–45
Previous studies have also reported higher rates of readmission for African-Americans with stroke, diabetes mellitus, and asthma.46
After adjustment for socioeconomic and clinical factors, we did not observe a significant difference in odds of readmission for black vs. white patients after colectomy. Interestingly, compared to white patients, Asian patients had higher odds of readmission, but lower odds of one-year mortality.
Other significant predictors of readmission included hospitalization in the year prior to surgery, higher comorbidity score, emergent admission, in-hospital complication, blood transfusion, and prolonged length of stay. Short duration of surgical hospital stay was not associated with increased readmission. However, we did observe a statistically significant trend of increased readmissions in later years. Our study period precedes the widespread implementation of “fast track” colorectal surgery protocols, and relatively few patients in our sample were discharged after hospital stays of four days or less. Future analyses should examine the impact of fast track protocols and laparoscopic surgery on the national early readmission rate after colectomy for cancer.
We found that low hospital procedure volume, but not low surgeon procedure volume, was associated with increased readmission as well as increased one-year mortality. Similarly, in their study of outcomes after primary colon cancer surgery, Schrag and colleagues concluded that hospital volume exerted a stronger effect than surgeon volume.14
Goodney et al. also studied the association between hospital volume and readmission after colectomy for cancer in a Medicare population. They concluded that the association between hospital volume and readmission, while statistically significant, was not clinically meaningful.5
In our study the difference in readmission rates in low compared to high volume hospitals (12% for the lowest volume tertile versus 10% for the highest tertile) was small but clinically significant.
An important finding of our study is that readmission was associated with increased one-year mortality. A similar association between readmission and increased mortality has been reported for patients with lung cancer treated with pulmonary resection.47
Conversely, readmitted patients with pancreatic cancer who underwent pancreaticoduodenectomy at Johns Hopkins actually had improved survival compared to patients who were not readmitted.48
In our study, the majority of factors that predicted readmission also predicted mortality. The observation that one-year mortality is higher for readmitted versus non-readmitted colon cancer surgery patients further supports the validity of readmission as a quality-of-care indicator.
Our study has several limitations. Because our study is limited to the Medicare population, the results may not apply to colon cancer patients younger than 65 years of age. However, the risk of colon cancer is known to increase with age, and the average age of diagnosis for patients with non-hereditary colon cancer is over 65 years.49
Also, because our study is based on claims data, we were unable to analyze clinical variables often used to assess “readiness for discharge,” such as patient symptoms, vital signs, laboratory values, bowel function, diet tolerance, and activity level. Claims data are also not well suited for the study of variables related to surgical technique, for example hand-sewn vs. stapled bowel anastomosis. Finally, other than marital status, our analysis did not include measures of social support, another factor that may influence the risk of readmission after surgery. It is likely that some of these factors which we did not measure are also important risk factors for early readmission after colectomy for cancer. Unmeasured factors may also be responsible in part for the observed association between readmission and one-year mortality.
Despite these limitations, this study has important implications. We have demonstrated that readmission after colon cancer surgery is common, readmissions cluster in the days immediately following discharge, and most causes of readmission are potentially preventable. This is the first study based on population-level data to identify multiple predictors of early readmission after colon cancer resection. While some significant predictors such as gender are not modifiable, others are related to structures and processes of care, such as hospital volume and blood transfusion. Importantly, our results show that early readmission is significantly associated with increased one-year mortality. Interestingly, many of the same variables that predicted readmission also predicted one-year mortality. We conclude that readmission is an important quality-of-care measure for colon cancer surgery. An understanding of the rate and predictors of readmission is a crucial first step in the process of developing targeted interventions that will reduce readmissions, decrease expenditures, and improve patient outcomes.